Quite frequently when a petroleum well is being drilled, and drill stem tests or core samples indicate that one or more stratums traversed by the hole are gas-bearing and/or oil-bearing stratums, the initial rate of flow from the stratum into the hole is far too low to warrant completion of the well. However, such signs, which would seem unpromising and downright discouraging to the uninitiated, are taken as signs for hope and encouragement to those skilled in the petroleum exploration, well-drilling, completion production and servicing fields. The basis for such hope and encouragement is the history of success built-up by those skilled in the art of production stimulation.
Production stimulation has many facets, because many different problems can be encountered at the interface of a bore hole with a petroleum-bearing stratum. Formation plugging due to depositing of the waxy constituents of the petroleum can be a problem, as can silting of the well due to influx of sand from a poorly consolidated stratum, and techniques have been developed for remedying these problems. At the other extreme from the foregoing, where flow at least initially is acceptably high but then is choked-off until a remedy is found, is the problem of tight formations, where the petroleum-bearing stratum naturally is relatively non-porous. However techniques have been developed for remedying this problem as well.
In some instances, e.g. where the oil and/or gas bearing stratum is calcareous, dolomitic acid-dissoluble rock such as limestone, the usual solution of the problem is to pump an inhibited hydrochloric acid solution down the well and out into the formation under high pressure. Then, after the inhibitor chemical which has protected the wellhead, casing and equipment as the solution was being pumped in decomposes, the acid attacks the stone, eating passages through it that will help petroleum to flow towards and into the well.
In other instances, for one reason or another, acidizing is not the answer or at least not the complete answer to curing a low flow rate stemming from tightness of the formation, and for such instances the technique of formation fracturing has been created and developed. In early, often successful attempts at formation fracturing, an explosive charge was lowered into the bore hole to the vicinity of the petroleum-bearing stratum and set off. The resulting concussion fragmented the rock and facilitated the flow of petroleum into the well from the surrounding formation. To a limited extent that mode of fracturing is still carried out. However, in the interests of greater control and better safety, formation fracturing is now more frequently accomplished by pumping a fluid down the bore hole and out into the formation. Then great pressure is applied to it for a substantial length of time, whereupon the pressure is released. As a result, the rock is fractured and the rate of flow of petroleum into the well often is substantially improved. As the fracturing fluid, often a liquid is used. Water and inhibited acid are examples of such working fluids; often propping agents such as sand, glass beads, pulverized nutshells or the like are carried in the liquid so that as the liquid is forced out into the formation and cracks opened up in the rock, the propping agent will invade the cracks and prevent them from closing. On other occasions, the fracturing fluid is a gas, e.g. a relatively inert gas such as molecular nitrogen.
Understandably, the companies and personnel which perform fracturing services are most interested in avoiding damage to equipment and injury or even the fear of injury to personnel as petroleum well formation fracturing is carried out.
In this connection, one stubborn and sticky detail which has often remained a problem, especially where the well is located in a remote area not served by convenient electrical power and an inert gas has been used as the fracturing fluid, is how, safely, to open the fracture valve to vent the gas to atmosphere after the high pressure has been held for the desired length of time. It is the rare person who would feel comfortable merely walking up to the wellhead and turning the fracture valve handwheel in such circumstances, yet heretofore that is exactly what someone often had to do.
The present invention provides a convenient means for actuating a valve such as a petroleum well fracturing valve from a remote, safe location.